1. Field of the Invention
The present invention relates to an image projection apparatus and a method of controlling the same.
2. Description of the Related Art
Conventionally, projectors are adapted to perform various processes in order to adjust the quality of an image to be projected. For example, a projector disclosed in Japanese Patent Application Laid-open No. 2002-156951 performs a process of changing the output of a lamp in accordance with the number of gradations of an input signal. More specifically, when a dark image is inputted into the projector, not only dark colors are displayed with image formation elements (such as liquid crystal devices and DMDs), but also a process of decreasing the output of the lamp is performed. By performing such processes, the number of gradations that can be expressed on a projection screen can be made into (the number of gradations that can be expressed with the image formation elements) multiplied by (a brightness range that can be expressed with the lamp).
A projector disclosed in Japanese Patent Application Laid-open No. 2000-131668 performs a process of changing the output of a lamp in accordance with the brightness of the room where the projector is used. For example, the lamp output is decreased in a dark room, whereas the lamp output is increased in a bright room. By performing such processes, a projection screen having appropriate brightness can be displayed.
However, in the aforementioned conventional technologies, the lamp output could be adjusted only in accordance with any one of two input values: a value indicating the brightness of the room where the projector is used; and a value indicating the number of gradations of an input signal. Accordingly, even when the lamp output was desired to be decreased in accordance with a dark image, the lamp output was sometimes increased according to a bright room. Thus, there were possibilities that the effects obtained by adjustment of the lamp were offset.
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an image projection apparatus that can appropriately adjust the output of a lamp in accordance with two input values: a value indicating the number of gradations of an inputted image; and a value indicating the illuminance of the room where the image projection apparatus is used.